JP5906085B2 - Method for improving content of useful components in plants in hydroponics - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing vegetables by hydroponics, and more specifically, vegetables by hydroponics in which the content of useful components such as antioxidant components, nutritional components, and taste components is increased and the nitrate nitrogen content is reduced. Relates to the production method.

  Hydroponics, which is a method of cultivating plants using nutrient solutions containing minerals and other ions without using soil, does not require farmland, as long as there is equipment, regardless of location or natural environment, It has the advantage that it is possible to cultivate plants under the proper conditions under the complete control of growth conditions such as nutrients, light, water, temperature, etc. It is widely used for the production of agricultural products such as vegetables because it can increase efficiency and easily adjust the harvest time.

  However, while vegetables grown by hydroponics grow quickly, there is a problem that the content of antioxidants such as ascorbic acid (vitamin C) and various nutritional components tends to be low. In humans, ascorbic acid is known to increase in demands by the body when stress such as flu and other infectious diseases is applied. With the increase in health consciousness, vitamin C is also included in vegetables. Higher quantities tend to be preferred.

  In addition to the above, nitrate nitrogen is usually contained in vegetables, but if it is contained in large amounts, it causes bitterness and may lead to the formation of carcinogens. Reduced vegetable production is desirable.

  Conventionally, studies have been conducted to increase the content of nutritional components including antioxidant components such as ascorbic acid in vegetables in hydroponics. For example, Japanese Patent Application Laid-Open No. 2004-305040 and Japanese Patent Application Laid-Open No. 2008-86272 (Patent Documents 1 and 2 respectively) have a peak near 315 nm in order to increase the content of functional components such as vitamin C and tocopherol. It is disclosed to perform artificial ultraviolet irradiation. However, such a method requires additional equipment including a specific ultraviolet lamp in addition to normal lighting, which increases costs and requires additional energy costs. There is a drawback that management is complicated.

JP 2004-305040 A JP 2008-86272 A

  Under the above background, the present invention eliminates the need for additional equipment including a special light source such as an ultraviolet lamp, and does not incur additional energy costs, so that useful components such as ascorbic acid, polyphenol, and sugar can be used. The object is to provide a method for producing hydroponic vegetables with increased content and reduced nitrate nitrogen content.

  As a result of the examination for the above purpose, the present inventor exposes a part of the root previously immersed in the nutrient solution to air for a certain period before harvesting in the final stage of hydroponics of vegetables. Found that the content of nutrients such as ascorbic acid, polyphenols and sugars (ascorbic acid and polyphenols are also antioxidants) and useful components such as taste components increased while the content of nitrate nitrogen decreased. The present invention was completed through further studies. That is, the present invention provides the following.

1. A method for producing a vegetable by hydroponics, wherein the vegetable is cultivated in a state where at least a part of the root is exposed to air for a predetermined period prior to harvesting the vegetable.
2. The production method according to 1 above, wherein the predetermined period is a period of 2 to 12 days.
3. The at least part of the root exposed to air extends over a length of 1 cm or more from the root origin or 3% or more of the total length from the root origin and from the tip of the root to less than 3% of the total length of the root The production method according to 1 or 2 above, which does not extend to the part.

  According to the present invention, there is no need for additional equipment including an ultraviolet lamp and the like, and the content of useful components such as nutritional components such as ascorbic acid, polyphenols and sugars and taste components is increased in a cost-effective manner, and nitrate nitrogen Hydroponic vegetables with a reduced content can be produced.

1 is a graph showing the ascorbic acid content of each plant in the control group and the rhizosphere partial exposure group in Example 1. FIG. 2 is a graph showing the sugar content (Brix) of lettuce in the control group and the rhizosphere partial exposure group in Example 1. FIG. 3 is a graph showing the nitrate nitrogen content of lettuce in the control group and the rhizosphere partial exposure group in Example 1. FIG. 4 is a graph showing the relationship between the exposure length of the rhizosphere partial exposure and the increase rate of ascorbic acid content in Example 2. FIG. FIG. 5 is a graph showing the relationship between the number of days of rhizosphere partial exposure treatment and the increase rate of ascorbic acid content in Example 3. FIG. 6 is a graph showing the polyphenol content of lettuce in the control group and the rhizosphere partial exposure group in Example 4. FIG. 7 is a graph showing the relationship between the number of days of rhizosphere partial exposure treatment and the rate of change in fresh weight of lettuce in Example 5. FIG. 8 is a graph showing the relationship between the number of days of rhizosphere partial exposure treatment and the rate of increase or decrease in the moisture content of lettuce in Example 5.

  In this specification, “hydroponic cultivation vegetables” refers to vegetables obtained by growing by hydroponic cultivation.

  In the present invention, for exposing at least a part of the root to the air (rhizosphere partial exposure treatment), for example, a container supporting the plant body on the nutrient solution surface is lifted from the nutrient solution surface or the nutrient solution surface is lowered. By maintaining the state, it is convenient to expose the root of the root to air, and the specific means for doing so are not limited.

  In the rhizosphere partial exposure treatment, the length of the portion of the root exposed to air (exposure length) is preferably 1 cm or more or about 3% or more of the total length of the root, more preferably 2 cm or more or the length of the root. It is about 6% or more of the total length, more preferably 4 cm or more, or about 13% or more of the total length of the root. However, it is necessary that at least a part of the root (preferably the tip) is immersed in the nutrient solution. In the case of the tip, if a portion corresponding to about 3% of the total length of the root is immersed in the nutrient solution Good.

  If the number of days of rhizosphere exposure treatment is too long, the effect will be diminished (because the plant will adapt to the cultivation environment in the state of exposure to the rhizosphere). The number of treatment days is preferably 2 to 12 days, more preferably 4 to 10 days, and even more preferably about 7 days.

  Because cultivation by rhizosphere partial exposure increases the content of useful ingredients such as nutrients and taste ingredients such as ascorbic acid, polyphenols, sugars, etc., because it is considered to be a basic defense response of plants against root air exposure stress, The method of the present invention can be widely applied to all vegetables.

  In this specification, “vegetables” includes “leaf vegetables”, “root vegetables”, and “fruit vegetables”. Here, “leaf vegetables” refers to vegetables whose leaves are edible, for example, lettuce, mizuna, spinach, spring chrysanthemum, komatsuna, chingensai, cabbage, Chinese cabbage, shiso, mustard vegetables, herbs (ruccola, basil) Etc.), but is not limited thereto. In addition, “root vegetables” refers to vegetables that eat parts of the ground such as roots and rhizomes, such as radish, carrot, turnip, burdock, potato, sweet potato, taro and lotus root. However, it is not limited to these. “Fruits and vegetables” refers to vegetables that use fruits and seeds as food, and examples include, but are not limited to, strawberries, tomatoes, cucumbers, and eggplants.

  In the present invention, nutrition in hydroponics, time distribution of light / dark period in one day, cultivation conditions such as temperature, and the number of days of growth until the rhizosphere partial exposure treatment may be appropriate. What is necessary is just to select suitably well-known various conditions and growing days suitable for vegetables.

  Hereinafter, the present invention will be described in more detail with reference to typical examples. However, the present invention is not intended to be limited by the description of the examples.

[Example 1] Rhizosphere partial exposure experiment in hydroponics of lettuce, mizuna, spinach, spring chrysanthemum and komatsuna Lettuce, mizuna, spinach, spring chrysanthemum, and komatsuna were hydroponically cultivated. The cultivation conditions were a white fluorescent lamp under a cycle of 14 hours light period / 10 hours dark period, and an aqueous solution of fertilizer (Otsuka House Fertilizer SA formulation) was used as a nutrient solution. The composition of the nutrient solution is as shown in Table 1 below.

  Seeds of the above plants are sown in a urethane medium, and irrigated 6 times / day at an irradiation intensity of 5,000 to 5,500 Lux, room temperature of 18 to 20 ° C., nutrient solution EC (electric conductivity) = 1.0 mS / cm, and grown for 5 days. After that, in submerged hydroponics, the plants are planted in a panel with the roots completely immersed in the nutrient solution, and the plant has an irradiation intensity of 13,000-18,000 Lux, a room temperature of 20 ° C., and a nutrient solution concentration of EC = 1.8 mS / cm. Depending on the conditions, it was cultivated for 13 to 26 days. The following table 2 shows the number of cultivation days from sowing to the day before the start of treatment for each plant.

  Various plants grown as described above were divided into two groups, and the plants of one group (control group) were cultivated for one week under the same conditions as before. For the plants of the other group (rhizosphere partial exposure group), the water level of the nutrient solution is lowered to provide a gap of 4 cm between the cultivation panel and the nutrient solution surface, and 4 cm on the root side of the plant body. The portion over the length was exposed to air in the gap, and cultivation was continued for one week in that state (rhizosphere partial exposure treatment). Next, harvested, and by the following method, ascorbic acid content and sugar content as an index of taste component as an index of nutrient components (and antioxidant components) in the plant body, and nitrate nitrogen content by the following methods, respectively. Measured and compared with those values in plants that did not undergo rhizosphere partial exposure treatment.

<Measurement of ascorbic acid content>
Method: A sample was crushed using a mixer while diluting a plant body with a certain amount of 5% metaphosphoric acid, and then the crushed liquid was centrifuged at 12,000 rpm for 1 minute. Using the supernatant liquid, the ascorbic acid concentration was measured with a reflection photometer RQflex (manufactured by Fujiwara Seisakusho), and calculated as the ascorbic acid content per 100 g of the plant body.

  Results: The results are shown in FIG. As seen in the figure, the ascorbic acid content of the plants subjected to the rhizosphere partial exposure treatment was 132% lettuce, 123% mizuna, 163% spinach, 148% spring chrysanthemum, 144% komatsuna when compared to the control group. It was proved that both increased remarkably. This shows that it is possible to increase the ascorbic acid content according to the invention in various vegetables.

<Measurement of sugar content (Brix (%))>
Method: 100 mL of water was added to the plant body and crushed with a mixer, and the crushed liquid was centrifuged at 12,000 rpm for 1 minute. The sugar content of the supernatant was measured using a pocket saccharimeter (PAL-1; manufactured by Atago), and based on this value, the sugar content (Brix (%)) was calculated as the weight percentage of sugar contained in the raw plant.

  Results: The results are shown in FIG. As shown in the figure, when the rhizosphere partial exposure treatment was performed on lettuce, the sugar content increased to 118% compared to the control group. This has shown that the content of the vegetable taste component can also be increased by this invention.

<Measurement of nitrate nitrogen content>
Method: Regarding the nitrate nitrogen content, the supernatant prepared in the above “Measurement of Ascorbic Acid Content” was diluted with a certain amount of water, and then, as in the case of ascorbic acid, the reflection photometer RQ Flex (Fujiwara) Measurement was carried out using a manufacturing method.

  Results: The results are shown in FIG. As seen in the figure, the rhizosphere partial exposure treatment reduced the nitrate nitrogen content to about 90% compared to the control group. This result shows that the nitrate nitrogen content of vegetables can be reduced by the present invention.

[Example 2] Examination of relationship between exposure length and content of useful components in rhizosphere partial exposure treatment In the rhizosphere partial exposure treatment, the gap between the panel and the nutrient solution surface is 0.5, 1, 2, 4, 5, 10 , 15, 20, 25, or 30 cm, the same method as in Example 1 except that the length of the root exposed to air (exposure length) was set to one of these lengths. Cultivated and harvested lettuce. The root length at the start of the rhizosphere partial exposure treatment was 30.9 cm on average, and in the group with an exposure length of 30 cm, the root tip was only slightly immersed in the nutrient solution. About the harvested lettuce, the ascorbic acid content was measured in the same manner as in Example 1.

  The results are shown in FIG. As seen in the figure, the ascorbic acid content did not change with respect to the control group at the exposure length of 0.5 cm, but by exposing 1 cm of the root (3.2% of the total root), It increased to 105%, further increased as the exposure length was increased, and increased to 125% or more at an exposure length of 4 cm or more. Even when an exposure length of 30 cm (97% of total roots) was exposed, the ascorbic acid content was increased to 130% of the control group. This result shows that the root of the plant body is exposed to air preferably 1 cm or more, more preferably 2 cm or more, more preferably 4 cm or more from the base, provided that at least 3% or more of the total length of the root is exposed on the tip side of the root. Cultivate for a period of about one week immediately before harvesting in a state where the length is immersed in a nutrient solution (ie, the exposure of the rhizosphere part does not reach less than 3% of the total length of the root from the root tip) This is effective in increasing the content of useful components such as nutritional components such as ascorbic acid and sugar and taste components in the plant body.

[Example 3] Examination of relationship between number of treatment days and useful component content in rhizosphere partial exposure treatment To examine the relationship between the number of days of rhizosphere partial exposure treatment and the useful component content of the plant, Example 1 above In the same manner as described above, lettuce seedlings were grown, then the exposure length was set to 4 cm, and the rhizosphere partial exposure treatment was performed for 0, 3, 7, 9, 12 or 14 days, the plants were harvested, and the ascorbic acid content was measured. .

  The results are shown in FIG. In the rhizosphere partial exposure group, ascorbic acid increased to 111% in the rhizosphere partial exposure treatment for 3 days compared to the control group, and further increased to the treatment for 7 days. However, after that, the rate of increase relative to the control group decreased, and the results of the 12-day treatment were equivalent to the 3-day treatment, and the 14-day treatment was equivalent to the control group and returned to the state before the increase in ascorbic acid. It was. This is probably because the plant has adapted to the cultivation environment with partial exposure to the rhizosphere. This result indicates that the number of days of rhizosphere partial exposure treatment is preferably 2 to 12 days, more preferably about 4 to 10 days, and even more preferably about 7 days.

[Example 4] Examination of effect of rhizosphere partial exposure treatment on polyphenol content In order to examine the influence of the rhizosphere partial exposure treatment on the polyphenol content of plants, lettuce was bred in the same manner as in Example 1 above. Then, the water level of the nutrient solution is lowered to provide a 4 cm gap between the cultivation panel and the nutrient solution surface, and the part extending over the length of 4 cm from the root of the plant root is exposed to the air. In this state, cultivation was continued for one week (rhizosphere partial exposure treatment). Next, the plant was harvested, and the polyphenol content in the plant body was measured by the following method.

<Measurement of polyphenol content>
10 g of 80% ethanol was added to 1 g of a sample obtained by freezing and crushing plant bodies in liquid nitrogen, left standing in a cool dark place for 2 hours, and centrifuged at 3000 rpm for 5 minutes to obtain a polyphenol extract.
The polyphenol content of the extract was measured by the foreign thiocult method. That is, 1 ml of a phenol reagent (MP Biochemical Co., Ltd.) diluted 1/2 was added to 1 ml of the extract and mixed. Further, 1 ml of 10% aqueous sodium carbonate solution was added, stirred and allowed to stand at room temperature for 60 minutes. Thereafter, the absorbance at 700 nm was measured with a spectrophotometer (UV-160; Shimadzu Corporation). Quercetin was used as a reference sample, and the polyphenol content in the sample was calculated as quercetin equivalent (mg quercetin / fresh weight).

  The results are shown in FIG. As shown in the figure, in the lettuce subjected to the rhizosphere exposure treatment, the polyphenol content increased to 151% of the control group. This indicates that polyphenol content is also improved by rhizosphere exposure treatment.

[Example 5] Examination of the effect of rhizosphere exposure treatment on the moisture content of plants As in the above experiment, the space between the cultivation panel and the nutrient solution surface is 4 cm, and the rhizosphere partial exposure for 3 to 14 days to lettuce Processed. After the treatment, the dry matter weight and fresh weight were measured to calculate the water content.
The results are shown in FIGS. As shown in FIG. 7, there was almost no negative effect on the growth of the rhizosphere partial exposure treatment for 3 to 10 days. However, the yield decreased by about 10% after 14 days of treatment. On the other hand, as shown in FIG. 8, the moisture content hardly changed during the treatment period, and it was found that there was no influence on quality such as texture.
Moreover, from this result, it is thought that the increase in the content of the nutritional component and the antioxidant component in the series of examples is not due to the concentration but the increase in the absolute amount. In addition, it was revealed that exposure of part of the roots to the air as described above for 2 to 12 days had no adverse effects on the yield (growth) and quality of the crop.

  The present invention makes it possible to produce hydroponically grown vegetables with an increased content of useful components such as ascorbic acid, polyphenols, and sugars in an inexpensive manner without the need for additional equipment such as ultraviolet lamps. Therefore, it is useful for producing vegetables that are rich in nutritional components and good in taste at a low cost.

Claims (1)

A method of producing vegetables by hydroponics, prior to harvesting of the vegetables, all SANYO, characterized in that a part of the roots over a period of 2 to 12 days to grow in a state of being exposed to air The part of the root that is exposed to air extends from the root root to 1 cm or more or from the root root to more than 3% of the total length and from the tip of the root to less than 3% of the total length of the root The production method is not as good as the part .

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